1. Field of the Invention
The invention generally relates to a supplemental inflatable restraint (SIR) system (or a so-called airbag system) for a vehicle and, more particularly, to a method and apparatus for use in the SIR system and for non-invasively classifying an occupant of a vehicle seat.
2. Description of the Prior Art
Various methods and apparatuses for use in such a SIR system and for classifying an occupant of a vehicle seat have been proposed so for.
For example, PCT (Patent Cooperation Treaty) patent WO99/38731 discloses “Evaluation method for a seat occupancy sensor”. The method comprises the steps of calculating an instantaneous occupancy profile with the use of measured values; comparing the qualities of the instantaneous occupancy profile with stored quality criteria; recording the instantaneous occupancy profile in a buffer storage if the instantaneous occupancy profile happens to superior in quality to the previous occupancy profiles; calculating an averaged occupancy profile by using the stored parameters; and classifying the seat occupancy with the established occupancy profile.
European patent EP0891898A1 discloses “Method and apparatus for recording various parameters of a person seat on a support”. The method involves determining the contact surface engaged on the underlay and determining the different parameters on the basis of the engaged contact surface, while taking account of the statistical correlation functions. The determining of the engaged contact surface includes the determination of the extension of the contact surface and the parameters (including weight or size class of the person) derived from this and the determination of the position of the engaged contact surface related to the underlay.
U.S. Pat. No. 5,732,375 discloses “Method of inhibiting or allowing airbag deployment”. The method determines whether the infant seat faces forward or rearward. The sensor load forces and the pattern of loading can identify an infant seat and determine its orientation. Local areas are checked to detect child occupants. Fuzzy logic is used to determine loading and to recognize patterns.
Japanese unexamined patent publication Nos. 2001-33324 and 2001-201412 assigned to the assignee of this invention disclose “Apparatus for determining occupant sitting in vehicle seat” and “Seating passenger number determining device of vehicle seat”, respectively. The former apparatus first classifies a vehicle seat occupant into two categories of a person and an infant seat on the basis of the relationship between the variance of the detected weights from seat sensors and the total detected weight and then, if the seat occupant is a person, classifies the person into an adult or a child. The latter device classifies a vehicle seat occupant into an adult, a child and an infant seat on the basis of correlation coefficients indicating the degree of agreement between the plane distribution shape of the detection load of each sensor and the reference load plane distribution shape.
However, the above-mentioned vehicle seat occupant classifying techniques are largely dependent on designer's intuition and experiences and disadvantageously fail to make the most of features contained in the detected values obtained from sensors of a vehicle seat. Also, designing a system according to any conventional vehicle seat occupant classifying technique requires a great deal of labor.
For this reason, what is needed is a vehicle seat occupant classifying technique that enables automated generation of a classifying algorithm and highly accurate classification of an occupant of a vehicle seat.